: My house is four years old. Six months after it was built, a second septic system was installed because the original was inadequate. I have used this newer system exclusively since then. The newer system has a pump which pumps sewage uphill to the second drainfield. Until recently, it has functioned without any sign of trouble. Recently, our toilets have begun to gurgle occasionally for less than a second at a time. The water level in the bowl does not seem to rise when this happens. It happens sometimes when taking a shower. Is this a cause for concern? Do I need to have my septic tank pumped out?

John, hope this helps.

Septic Tank Pumping Guide

Find Here: When should septic tanks (onsite sewage disposal system holding tanks) be pumped? Why? What causes failures?Links to more in-depth information. Having surveyed and collected septic system design and testing information from many U.S. states and Canadian Provinces, Ithink that information provided by the Penn State College of Agriculture - Cooperative Extension is clear and representative ofexpert thinking on this topic. For clarity and content I've made minor edits to the original material.

The most common domestic wastewater treatment system used in rural areas is the septic tank-soil absorption system. Theseptic tank removes settleable and floatable solids from the waste water. The soil absorption field then filters and treats theclarified septic tank effluent and distributes it through the soil. Removing the solids from the wastewater protects the soilabsorption system from clogging and failure. In addition to removing solids, the septic tank also promotes biological digestion ofa portion of the solids and stores the remaining undigested portion.

The first stage of the treatment system, the septic tank, removes solids by holding wastewater in the tank. This allows theheavier solids to settle as sludge and the lighter particles to form scum at the top. To accomplish this, wastewater should be heldin the tank for at least 24 hours. Up to 50 percent of the solids retained in the tank decompose; the remainder accumulate in thetank. Biological and chemical additives are not needed to aid or accelerate decomposition.

As the system is used, sludge continues to accumulate in the bottom of the septic tank. Properly designed tanks have enoughspace for up to three years safe accumulation of sludge. When the sludge level increases beyond this point, sewage has less timeto settle before leaving the tank and more solids escape into the absorption area. If too much sludge accumulates, no settlingoccurs before the sewage flows to the soil absorption field. Infiltration of sludge into the soil absorption field can cause systemfailure. To prevent this, the tank must be pumped periodically. The material pumped is known as septage. This figure shows atank in cross-section, but you don't need to look at it to understand the text below. For more septic system illustrations seeSeptic System Illustrations.

The frequency of pumping depends on several factors:

1.capacity of the septic tank 2.volume of wastewater (related to size of household) 3.amount of solids in wastewater (e.g. garbage disposals produce more solids)

Table I lists estimated pumping frequency according to septic tank capacity and household size. The frequencies werecalculated to provide a minimum of 24 hours of wastewater retention assuming 50 percent digestion of the retained solids.

* Below the minimum size allowed in Pennsylvania and other jurisdictions

Note: More frequent pumping is needed if a garbage disposal is used. Generally the indicated frequency will vary with thevolume of solids (+20% for high volume, -20% for low volume).

Under current Pennsylvania law a 900 gallon septic tank is the minimum size that must be used for a home with three bedroomsor less. If six people reside in a three-bedroom house, the tank should be pumped every 1.3 years. If the same system serves afamily of two, the tank would be ready for pumping every 5.2 years. Systems installed before the current rules and regulationswere implemented may need to be pumped more often, perhaps every year or less.

As indicated in the footnote to Table 1, garbage disposers will increase the frequency of pumping. For example, if this samethree bedroom house with six residents had a garbage disposal and was generally producing a higher volume of wastewater, thepumping frequency would be calculated as follows:

1.3 years - [(0.2) x 1.3 years] = 1.0 year

If you have just moved into a home, you may not know the size of the tank. In this case, you should have the tank pumped andinspected. The company pumping the tank will tell you its size, age, and condition.

Septic tanks will not fail immediately if they are not pumped. However, an un-maintained septic tank is no longer protecting thesoil absorption field from solids. Continued neglect may result in system failure and even replacement of the soil absorption field.In some cases, site limitations may make replacement of the absorption field impossible. If system replacement is the onlyoption, contact your local Sewage Enforcement Officer (SEO) or municipal sanitarian or health department since a permit forthe new system will be required.

More explanation: In order for a tank to function properly, adequate liquid volume must be maintained to allow for sufficient"settling time" which permits solids to either settle out as sludge or join the floating-scum layer at the top of the tank. Baffles inthe tank prevent the floating scum from leaving the tank, an event which would lead to rapid failure of the absorption system.When pumping is too infrequent, even if the tank is not totally clogged with solids, the reduced liquid volume in the tank cutssettlement time and forces small floating solids out to the absorption system, shortening its life.

Cleaning Septic Tanks

Septic tank pump and haul contractors can clean your tank. It is a good idea to supervise cleaning to assure that it is doneproperly. To extract all the material from the tank, the scum layer must be broken up and the sludge layer mixed with the liquidportion of the tank. This is usually done by alternately pumping liquid from the tank and re-injecting it into the bottom of thetank. The septic tank should be pumped through the large central manhole, not the baffle inspection ports. Pumping a tankthrough the baffle inspection ports can damage the baffles, resulting in a destroyed leach field.

The use of additives in septic tanks to reduce the sludge volume or substitute for pumping is not recommended. In fact, relyingon additives rather than conventional tank pumping may result in failure of the septic system. Septic additives are illegal in manyjurisdictions.

Before closing the tank, check the condition of the baffles. If they are missing or deteriorated, replace them with appropriatesanitary tee baffles. It should never be necessary to enter a septic tank. Any work to replace the baffles or repair the tankshould be done from the outside. Decomposing wastes in the septic tank produce toxic gases which can kill a human ina matter of minutes. When working on a tank be sure the area is well ventilated and that someone is standing nearby. Nevergo into a septic tank to retrieve someone who has fallen in and was overcome by toxic gases without a self-contained breathingapparatus (SCBA). if a SCBA is not available, call for emergency services and put a fan at the top of the tank to blow in freshair.

To facilitate future cleaning and inspection, install risers from the central manhole and inspection ports to the surface beforeburying the tank Also mark the location of the tank, so it can be easily identified.

Summary

The septic tank is only one part of an on-site wastewater system. It is designed to remove solids prior to the effluent entering thesoil absorption field, provide for the digestion of a portion of those solids, and store the remaining solids. Biological andchemical additives are not needed to aid or accelerate decomposition. Garbage grinders impose an additional solids load on thesystem. Solids must be removed periodically to prevent them from entering the soil absorption field. For a properly designedseptic system, the tank should be inspected and pumped every 1 to 5 years.

More Information

Other Penn State Fact Sheets relating to domestic wastewater treatment systems include